The risk of damage to property or injury to persons due to collisions of persons or property with merchandise carts or the like travelling at excessive speeds has long been recognized. This risk is especially prevalent when such merchandise carts are used by customers of supermarkets and other retail stores to transport their purchases across the parking lot to their automobile. Due to prevailing construction practices, terrain, or for purposes of drainage, such supermarket and retail store parking lots are often constructed on an incline. If a person accidentally loses control of a cart full of groceries or other merchandise, the cart can gain considerable speed and momentum travelling down such an incline. Furthermore, even when a customer successfully unloads the cart safely, the danger remains, because quite frequently the cart is left in the parking lot at the location where it was unloaded. The unattended cart may then begin to roll down the incline, or even be blown by the wind. The danger of a collision of such a runaway cart, whether loaded or unloaded, with an automobile parked in the parking lot or a person walking in the parking lot is apparent.
A number of wheel brakes have been proposed to deal with such problems. Many conventional brake mechanisms have required the customer to manually operate a hand brake. However, such manual brakes are inconvenient, and the customer cannot always be relied upon to set the brake when the cart is left on the lot after unloading.
U.S. Pat. No. 3 771 628 addresses some of these problems, by providing a brake mechanism which automatically engages when the speed of the cart exceeds a predetermined maximum. After the brake engages, rotation of the wheel is retarded until the cart is gradually brought to a halt. This device frees the customer from the inconvenience of using the hand brake, and also provides for gradually stopping a runaway cart which exceeds the predetermined maximum speed. However, such a speed responsive wheel retarder has the following problems. If the maximum speed of the cart is set too high, a runaway cart may well travel a great distance down the incline before it gathers enough speed to engage the wheel retarding mechanism. Having travelled such a great distance, the cart is likely to be near automobiles or persons in the parking lot before the wheel retarding mechanism engages. Because the wheel retarding mechanism in the above-mentioned patent only brings the cart to a gradual stop, it may not be able to stop the cart before a collision occurs. Even if the cart, upon reaching such a high speed, has not drawn near persons or automobiles, a collision may not be avoidable because gradual braking requires more distance to effect a stop when speeds are high. It is therefore desirable to provide a wheel brake means which will allow customers to make any reasonable use of the cart, and which acts continuously to prevent the wheels from achieving an undesirably high rotational speed, thereby avoiding the problem of high speed braking.
Accordingly, the objects of the invention include:
1. To provide a friction wheel brake which continuously acts to prevent a wheel from achieving an undesirably high rotational speed;
2. To provide a friction wheel brake, as aforesaid, which does not interfere with any reasonable use of a merchandise cart;
3. To provide a friction wheel brake, as aforesaid, which is easily adjustable to varying braking forces; and
4. To provide a friction wheel brake, as aforesaid, which is inexpensive and durable.